Histologic study at the level of light and electron microscopy of normal and pathologic human inner ear and spiral ganglion is proposed. The specific aims include: 1. Completion of a serial section study of a case of Meniere's disease, including statistical analysis of the number of afferent endings at the base of inner and outer hair cells, the neuronal density at the level of the osseous spiral lamina and at the level of spiral ganglion. 2. Initiating a qualitative and qualitative analysis of the human spiral ganglion by serial section analysis and 3D reconstruction. After normative data is obtained, this analysis will be extended to pathological cases which have been already obtained and to specimens anticipated. 3. Continued study of human temporal bone material already obtained in the pervious grant period. The acquisition of human temporal bones has exceeded our capacity to study them by electron microscopy and there are several cases with audiometric documentation which have yet to be studied. 4. Continued accrual of temporal bones with audiometric documentation and of sufficiently good fixation for electron microscopy. The exact nature of study will obviously depend in large measure on pathology obtained in these cases. Temporal bones are obtained through the Pathology Departments of the affiliated hospitals and through the National Temporal Bone Bank. Specimens are fixed in situ and removed in the Pathology Department and prepared for light and electron microscopy. Analysis of material obtained would be largely by serial section reconstruction and 3D reconstruction as needed. There is a growing body of data suggesting that the normal ultrastructural anatomy of the human inner ear, both at the level of the organ of Corti and at that of the spiral ganglion, is significantly different from that of the usual mammalian models. Further documentation of these differences as well as pathologic changes seen in the human will be of use in interpreting animal models of hearing loss, understanding of human diseases of the inner ear, and providing a rational foundation for treatment of human hearing loss.